[clang] [clang-tools-extra] WIP: Extend SourceLocation to 64 bits. (PR #146314)

[Erich Keane via cfe-commits]

erichkeane wrote:

> > I did a light pass of the 1st 1/4 of this or so. The smuggling back and forth to raw-encoding seems strange? WHy are we doing that here?
> 
> In this patch, to keep AST node size as small as possible, we're using 40 bits of `StmtBits` to store the SourceLocation, we need this back-and-forth conversion.
> 
> For the `DeclarationName`, you're right — we can just store the SourceLocation directly and avoid the raw-encoding round-trip.

Sorry for being dumb... how are we getting away with only storing 40 bits?  Does that not just artificially limit our source-location size for statements?  And, frankly, then our entire space?  I guess 8 2x-increases in source-location size are nice, but I was sort of hoping the switch to 64 bits meant we never had to discuss this again for the rest of my life:D 

https://github.com/llvm/llvm-project/pull/146314